recluster

Clustering library with support for zero-downtime reloading

usage

If server.js is your regular http server (e.g. express), create
cluster.js and add:

``js
var recluster = require('recluster'),
path = require('path');

var cluster = recluster(path.join(__dirname, 'server.js'));
cluster.run();

process.on('SIGUSR2', function() {
console.log('Got SIGUSR2, reloading cluster...');
cluster.reload();
});

console.log("spawned cluster, kill -s SIGUSR2", process.pid, "to reload");
`

then run it

node cluster.js

To hot-reload the server, simply run

kill -s SIGUSR2

To find out which of the N (= number of cores by default) worker
instances you're running from inside server.js, you can use

process.env.WORKER_ID

which is zero-based i.e. 0 <= WORKER_ID < N

options

`js
var cluster = recluster(file, opt)
`

where

$3

Absolute path to the module that defines the server

$3

Number of active workers (default = cores)

$3

Timeout to kill old workers after reload (seconds).

Defaults to 1 second in development, 1 hour in production.

$3

Minimum time between worker respawns when workers die (seconds)

$3

Maximum respawn time (reached via exponential backoff). Set to
0 or undefined to disable exponential backoff.

$3

Use 'listening' for servers (e.g. for express/connect http servers)
and 'started' for workers that are immediately ready.

If you want to manually tell recluster when the worker is ready to replace
older workers you can use {readyWhen: 'ready'}. Then, to signal readiness
from the worker use process.send({cmd: 'ready'})

$3

Array of arguments to pass to the worker

$3

Log various events to stdout. Currently only 'respawns' is supported.
Default: {respawns: true}

$3

Which logger to use. Requires a console-compatible log method
Default: console

cluster

The returned object has the following methods:

$3

Starts the cluster by running child processes

$3

Hot-reloads new code. some of the children will remain active
for opt.timeout seconds after reload

$3

Terminates the entire cluster and removes all listeners.

$3

Returns a hash of all worker slots (0 <= WORKER_ID < N). If a worker isn't
available at that slot, the value in the hash is null or undefined. Otherwise,
the value will be a worker object that is ready to serve requests.

$3

Returns an array of all the workers, including those that are not
yet ready or those that will be replaced.

worker cleanup

A server worker can gracefully exit by cleaning up in the 'close' event
of its server:

`js
server.on('close', function() {
// cleanup
});
`

Non-server workers can listen for the disconnect command and shut down
gracefully before the kill timeout:

`js
process.on('message', function(m) {
if (m.cmd == 'disconnect') {
// cleanup
}
})
``

sticky sessions support

If you need sticky sessions e.g. for socket.io you can use the experimental
companion module [sticky-listen][sticky-listen], which implements an alternate
balancer that distributes the sockets based on the client IP (instead of the
regular round-robin one)

[sticky-listen]: https://github.com/spion/sticky-listen

!Bitdeli